Tobacco denicotinization process

ABSTRACT

A method for denicotinizing and/or mellowing tobacco by treating the tobacco with a gaseous treatment medium containing at least water vapor and/or at least ammonia wherein there is contemplated controlling the process conditions, especially when working with an ammonia-containing treatment medium controlling the quantity of ammonia added thereto and, during an exclusive or subsequent treatment with an ammonia-free water vapor-containing treatment medium controlling the termination of the tobacco treatment on the basis of the pH-value and/or the titration value of the condensate of the treatment medium leaving the treated tobacco.

United States Patent [191 Egri [111 3,821,960 July 2,1974

[ TOBACCO DENICOTINIZATION PROCESS [75] Inventor: Laszlo Egri, Basel, Switzerland [73] Assignee: Tamag Basel AG, Birsfelden, Switzerland [22] Filed: Nov. 5, 1971 [21] Appl. No.: 195,960

Related US. Application Data [63] Continuation-impart of Ser. No. 823,508, May 9,

1969, abandoned.

[30] Foreign Application Priority Data May 13, 1968 Switzerland 7072/68 [52] US. Cl. 131/143 [51] Int. Cl A24b 15/02 [58] Field of Search 131/143, 140

[56] References Cited UNITED STATES PATENTS 1,671,259 5/1928 Schloesing l3l/l46 3,l39,435 6/l964 Staleyet al. 13l/l43 X NH 65C 12' I Fractions 3.399680 9/l968 Egri l3 1/134 FOREIGN PATENTS OR APPLICATIONS 714,867 8/]965 Canada l3l/l43 Primary ExaminerMelvin D. Rein Attorney, Agent, or Firm-Werner W. Kleeman 5 7] ABSTRACT A method for denicotinizing and/or mellowing tobacco by treating the tobacco with a gaseous treatment medium containing at least water vapor and/or at least ammonia wherein there is contemplated controlling the process conditions, especially when working with an ammonia-containing treatment medium controlling the quantity of ammonia added thereto and, during an exclusive or subsequent treatment with an ammonia-free water vapor-containing treatment medium controlling the termination of the tobacco treatment on the basis of the pH-value and/or the ti- 1 tration value of the condensate of the treatment medium leaving the treated tobacco.

28 Claims, 6 Drawing Figures 65 m I S P Nicot ine Nl otme PATENTEUJUL 21914 332L960 Fig.7. Fig/6 Nicotine 12 NICO no Fractions Fractions Fig.2. 0 F1926 PH 65 C mg PH 55C v NR 65C g vp Nicotine NH 65C (lowerp M me NI otme #12345678910 12345s7s9io Fractions Fractions Fig. 6 mg NH: F1936,

P 65 80 22. 3 55 80c 65C 80c 65C PH Nicotine 12 rack Fractions Fractions 1 TOBACCO DENICOTINIZATION PROCESS CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part application of my commonly assigned, copending United States application, Ser. No. 823,508, filed May 9, 1969, now abandoned and entitled METHOD FOR TREATING TOBACCO.

BACKGROUND OF THE INVENTION The present invention relates to a new and improved method for treating tobacco, and especially concerns itself with the denicotinizing and/or mellowing of tobacco.

By virtue of the teaching set forth in US. Pat. No. 896,124, granted Aug. 18, 1908, and listing as the inventors G. B. Lindenberger and R. B. Arnold, it has been known for quite some time that it is possible to reduce the nicotine content of tobacco by treating such with a gaseous medium containing, if desired, steam, treatment preferably taking place at elevated temperatures.

However, it was not long until it was determined that when utilizing this technique, in principle constituting a steam distillation technique, it was possible to only remove a very slight proportion of the nicotine present in the tobacco, namely the nicotine existing in the form of a free base.

Therefore, as for instance disclosed in the US. Pat. No. 999,674 granted on Aug. 1, 1911 to J. Sartig and US. Pat. No. 1,671,259, of Schloesing, attempts were made with a certain degree of success to free the nicotine from the nicotine salts by moistening the tobacco with an ammonia solution prior to the steam treatment, thereby obtaining a more extensive denicotinization. However, this technique is neither economically completely satisfactory nor does it render possible sufficient denicotinization of the tobacco.

Even if a practically complete separation of the nicotine, as a general rule, is only then of decisive importance if there is to be obtained as the primary product nicotine and not a tobacco suitable for smoking having a reduced nicotine content, still, with these techniques what is disturbing is the limits which can be drawn with regard to the thereby obtainable degree of denicotinization, especially the frequently occurring loss in aroma of the treated tobacco.

A more efficient method in this connection is, for instance, taught in an Austrian Pat. No. 147,672 and the previously mentioned US. Pat. No. l,67l,259. When working with these known procedures ammonia in gaseous form is added to the steam-' or water vaporcontaining treatment medium. However, apart from the difficulties in working at optimum conditions throughout all phases of the treatment, this technique is associated with the decisive disadvantage that the obtained tobacco product is, in certain instances, so sharp, that is, produces such a sharp and bitter or acrid tasting smoke, that as a practical matter it can not be used as smoking tobacco.

As has become known to the art, for instance, from US. Pat.'No. 2,136,485, granted Nov. 15, 1938 to F. Berka and A. Giller, attempts have been made,'while using a treatment medium containing steam and ammonia gas, to free the denicotinized tobacco from excess ammonia by subjecting such to an aftertreatment with an ammonia-free treatment medium, as a general rule containing steam.

Due to such type aftertreatment or post-treatment there is obtained a mellowing of the tobacco, which in any event is absolutely necessary for tobacco which has been denicotinized by a treatment medium containing ammonia, and sometimes however also for untreated tobacco which is particularly sharp, in order to obtain a marketable product, that is, a tobacco which will not be rejected by the smoker as too sharp.

Unfortunately, when resorting to such mellowing treatments, this likewise being the case for allof the previously mentioned denicotinizing techniques, there results a more or less pronounced impairment of the taste and/or aroma of the treated tobacco, the degree of which, similar to the denicotinizingand/or mellowing effect strived for by such treatment, is dependent upon numerous process parameters which cannot be exactly predetermined, especially upon temperature, pressure, composition of the treatment medium, the treatment duration, the type of tobacco treated, and the apparatus employed in the treatment.

The resultant danger of too intensive treatment, in other words overtreatment, oftentimes producing a strawy" or flat tobacco, has been attempted to' be mitigated through the use of treatment conditions which are as protective as possible, for instance by working at reduced pressure and at temperatures which are as low-as possible. While this produced certain improvements such did not however provide a solution of the problem which could really be considered satisfactory in practice. One of the primary difficulties in the selection of suitable parameters and conditions for the denicotinizing and/or in particular tobacco mellowing previously resided in the fact that during treatment, while it was possible to determine relatively quickly the degree of denicotinization reached at any given period of time by knowing the starting nicotine content and the quantity of tobacco processed as well as by determining rather rapidly up to a certain point during the course of treatment the quantity of extracted nicotine, still it was not possible to determine the stage of treatment which had been reached for the treated tobacco as concerns its sharpness and other taste-and aroma properties. The latter situation was particularly extremely disturbing, since it was not possible to reliably select on the basis of experience suitable values for the treatment conditions, especially an appropriate treatment duration, because identical treatment conditions produced non-predictable differing results and because tobacco as a product of nature possesses different properties from one supply to the next, even in fact at times from one bale to the next.

The taste characteristics of tobacco at a certain period of time during treatment for a long time previously could only be determined by organoleptical checking of a test sample removed at'that given period of time and checked by very time-consuming test procedures, as well as in certain cases by carrying out a pH-value measurement-of the smoke condensate obtained by smoking special test cigarettes or cigars in complicated smoking machines and which test cigarettes or cigars were produced from samples of the tobacco. In other words, methods had to be resorted towhich only gave results after a long time delay, so that as a practical matter these techniques could not be seriously considered for controlling the treatment of tobacco for denicotinization and/or mellowing purposes.

OBJECTS OF THE INVENTION Hence, it is a primary object of the present invention to provide a new and improved method for the denicotinization and/or mellowing of tobacco suitable for smoking purposes, by treating the tobacco with a gaseous treatment medium containing steam and/or ammonia, wherein on the basis of certain characteristic values which can be easily and rapidly determined the treatment conditions can be controlled in such a manner that:

a. denicotinization can be optimumly carried out, that is, as rapidly as possible until reaching a desired degree of denicotinization and under the best possible utilization of the active component(s) of the treatment medium and/or b. mellowing is carried out protectively, effectively and while preventing overtreatment and providing reproducible results.

A further significant object of the present invention I is to provide a new and improved method of treating tobacco and, in particular, controlling the mellowing thereof, such that the tobacco products obtained through the practice of the inventive method posesses a much better quality than tobacco obtained by treatment techniques wherein mellowing is not controlled.

A further object of this invention is to provide a method of treating tobacco'wherein the addition of ammonia is controlled during denicotinization in a manner resulting in a reduction in the ammonia consumption and increased economies in the treatment process.

Still a further significant object of the present invention resides in treating tobacco in a manner providing a decrease in the consumption of steam during mellowing of the tobacco and also affording reproducible results, so that the treated tobacco products even from one charge to the next, are relatively uniform in quality as desirably required for marketing purposes.

SUMMARY OF THE INVENTION Now it has been surprisingly found that a certain correlation exists between the pH-value and/or the titratable base content of the condensate of the treatment medium leaving the treated tobacco and the course of the treatment, as well as also with regard to the efficiency of denicotinization and the characteristics of the treated tobacco. This correlation renders it possible to determine or follow the course of the treatment on the basis of relatively simple and quickly ascertainable analysis data, namely the pH-value and/or the titration value of the condensate of the treatment medium. leaving the treated tobacco and thereby appropriately controlling the actual treatment.

Accordingly, the invention proposes an improved method for the denicotinization and/or mellowing of tobacco by treating the tobacco with a treatment medium containing at least steam and/or at least ammonia and steam in that, during treatment there is determined either continuously or periodically the pH-value and/or the titration value of the'condensate of the treatment medium leaving the treated tobacco, and treatment of the tobacco on the basis of the determined data is controlled in such a manner that:

a. during an eventual treatment with an ammonia containing treatment medium, the treatment conditions, especially the introduction of the ammonia, is regulated in such a fashion that the pH-value of the condensate is between approximately 10.5 and 12 and- /or the titration value of a 10 ml sample of the condensate is between approximately 45 ml and approximately 80 ml 0.1 n H 50 and/or b. In the event mellowing is undertaken by treatment with an ammonia-free treatment medium, the initially the tobacco is treated under defined conditions, especially with regard to temperature, flow velocity, and pressure of the treatment medium, with an' ammoniafree steam or water vapor-containing treatment medium, and the pH-value and/or the titration value of the condensate, obtained by condensing the treatment medium, is determined as soon as possible following the establishment of stable conditions, (these values constituting the reference-pH and reference titration value). The sole or last treatment with an ammonia-free, steam-containing treatment medium is then terminated when, under the treatment conditions employed for the determination of the reference pH value and/or reference titration value, the pH-value of the condensate is in a range of approximately 1.0 unit of pH value beneath the reference pH value as determined above up to approximately 0.5 unit of pH value above such reference pH and/or the titration value amounts to between and l 10 percent of the reference titration value, and further, under the condition that, if the tobacco after the determination of the reference pH value and/or the reference titration value as explained above, has not been treated at least one time with an ammonia containing treatment medium, then treatment is interrupted at the earliest if, under the same treatment conditions as prevailed for the determination of the reference values, the pH-value of the condensate is at least approximately 0.1 unit of pH lessthan the reference pH value and/or the titration value of the condensate is at least approximately 5 percent smaller than the reference titrationvalue.

The titration values refer to the condensate emanating from approximately 100 kg tobacco after throughpassage of the treatment medium at approximately 60C C and with a velocity of l-2 kg/min.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof.

FIGS. 1a, 1b, 2a, 2b, 3a and 3b are respective graphs serving to elucidate the method aspects of the invention in the practice of treating tobacco as taught herein.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE PRESENT INVENTION As will be recognized from the preceding discussion, the invention relates to an improvement in the method of treating tobacco for consumption purposes, wherein the tobacco is subjected to a treatment producing either only denicotinization, only mellowing, or, however, both denicotinization aswell as mellowing, at least to a degree beneath the increased degree of tobacco sharpness which is unavoidable when carrying out denicotinization with an ammonia-containing treatment medium. Tobacco Denicotinization As will be more fully appreciated from the various illustrative examples given hereinafter and the comparative tests, it has been found that a better, that is to say, a more rapid denicotinization can be attained if, while using the otherwise similar treatment conditions, initially a treatment medium containing ammonia and steam or water vapor, and then following a certain amount of time a steam-containing, ammonia-free treatment medium is permitted to flow through the tobacco, instead of allowing for a certain period of time initially a stationary steam-containing and ammoniasaturated atmosphere to act upon the tobacco to be treated and then to treat such with a flowing steamcontaining, ammonia-free treatment medium.

Furthermore, it has been found that the speed of denicotinization, which of course more or less rapidly drops during the course of the treatment as a function g of the decreasing nicotine content of the treated tobacco, among other things is considerably dependent upon the concentration of the ammonia in the treatment medium. Whereas, however, the prior publications in this particular art, as concerns the dosage of ammonia, previously merely proposed roughly using approximately a 2 to 3-fold excess of ammonia, basedupon the quantity of ammonia required for freeing the bound nicotine in the tobacco present in the form of salts, it has been determined in accordance with the teachings of this invention, as likewise will be more fully demonstrated by the hereinafter given examples and comparative tests,that such a rough control of the denicotinization with an ammonia-containing treatment medium does not reliably lead to a treatment which is as economical as possible, wherein the employed ammonia is optimumly utilized and for the prevailing remaining operating conditions results in the best possible denicotinization speed.

Instead, it has been found that in order to attain an optimum'control of the process during denicotinization, it is much more the case that it is important to continuously 'or from time to time determine the pH- value of the condensate of the treatment medium leaving the tobacco undergoing treatment and/or the titratable base content of the aforementioned condensate and with other constant process conditions, such as temperature, pressure, flow velocity of the treatment medium and so forth, to regulate dosing of the ammonia in such a way that the pH-value of the condensate I is between approximately 1 1.0 and 12.0, preferably between approximately ll.2 and 11.8. Denicotinization occurs especially favorably then if the pH-value of the condensate is in a range of about 1 1.5 to l 1.8, and especially then if such pH-value is preferably at approximately 1 1.7. As has been determined by experiments, the denicotinization speed for condensate pl-l-values of less than approximately 11.6 to 11.7 always increasingly drops, whereas pH-values greater than approximately 1 1.7 can only be achieved through an extraordinarily high increase in the ammonia concentration of the treatment medium, without thereby, however,

. achieving a further increase or at least any appreciable further increase in the denicotinization speed. Instead of, or in addition to, the pH-value of the condensate it is also possible to determine its titration value and to use such for controlling the treatment conditions during denicotinization, especially to makeuse of such titration value for controlling the dosage of ammonia. However, the determination of the titration value is much more difficult to arrive at and much more timeconsuming than the determination of the pH-value which can be continuously carried out with conventional pH-measuring devices. Furthermore, the increased accuracy of the titration value as well as the thereby more exact control possibility of the treatment conditions during denicotinization is not absolutely necessary in order to obtain a sufficiently economical process, so that the control of the treatment during tobacco denicotinization is preferably undertaken merely as a function of the pl-l-value of the condensate. However, by way of completeness in the disclosure of the method aspects of this development, the titration value ranges, within which it is possible to practice the teachings of the present invention process, will be given. As already explained, during denicotinization the titration value of a 10 ml condensate sample should be in the range of 45 to 80 ml 0.1 normal sulfuric acid (H 80 It is preferable to operate under conditions at which this titration value is in a range of about to ml 0.1 normal'sulfuric acid.

Finally, with respect to the denicotinization operation it has been found that the average denicotinization speed and therefore the degree of total denicotinization which can be obtained with a denicotinization treatment extending over a certain time period can be considerably increased if, instead of carrying out a continuous treatment, that is a treatment under essentially constant conditions, wherein if desired there can be carried out a subsequent treatment with an ammoniafree, steam-containing treatment medium, there is carried out a so-called pulsating treatment, wherein from time to time the temperature of the treatment medium is briefly increased for short intervals. With the inventive preferred employed pulsating treatment it is especially advantageous, during the treatment phases at relatively low temperatures, to add ammonia to the treatment medium, the ammonia being absorbed much better by the tobacco undergoing treatment at the relatively low temperatures than at the higher temperatures, and therefore to provide for a more complete and effective utilization thereof. Further, during the treatment phases undertaken at the higher tempera tures there is advantageously introduced into the treatment zone an essentially ammonia-free, steamcontaining treatment medium. The so-called pulsating treatment is especially then advantageous if it is desired to obtain as the essential or singular product not nicotine, rather a tobacco suitable for smoking purposes,

since in this case it is especially advantageous to maintain the total treatment time as short as possible and on the average to work with conditions which are as mild or protective as possible, that is to say, to especially work at as low an average temperature as possible in order to maintain losses in aroma of the tobacco as low as possible which cannot be avoided in any event when carrying out such treatment.

As concerns the duration of the individual treatment steps or phases during such pulsating treatment as well as the most favorable increase of the thus to be employed temperature increments or jumps there cannot be really formulated any generally valid rules, since the course of the treatment in this case is dependent upon too many conditions. However, the course of the pH- value curves, especially in combination with the denicotinization curves which can be determined by employing known techniques, and as will be more fully explained in detail hereinafter in conjunction with the examples, nonetheless provides a certain guideline or starting point, whereby especially the transition from a high temperature treatment phase to the next lower temperature treatment phase can be determined on the basis of the pH-value curve of the condensate, since, as will be appreciated from what will be explained hereinafter, from the pH-value curves portrayed in FIGS. 4a and 4b, during a pulsating denicotinization treatment during the high temperature phases there can more or less always be ascertained a rather pronounced curved knick or bend, from which point on the initially relatively rapid dropping of the pH-value slows down, whereby approximately at the same time there is a reduction in the denicotinization speed. Experience has shownthat it is particularly advantageous to interrupt the high temperature phase and to switch over to a new lower temperature phase when, following the occurrence of the previously mentioned bend in the curve of the pH-value, approximately the same time has expired as existed between the beginning of the relevant high temperature phase and the occurrence of such bend in the pH-value curve.

With the method of the invention in order to obtain as intensive as possible treatment effect one should work at as-high temperatures as possible, whereas in consideration of providing as protective as possible treatment of the tobacco material and in order to obtain optimum utilization of the employed ammonia the treatment should be carried out at the lowest possible temperatures.

In practice one should not fall below a treatment temperature which is in the range of 40C to 50C so as to prevent excessively long treatment times. On the other hand, at least then when treating especially sensitive and aromatic tobaccos a maximum temperature of approximately 100C should not be reached, or at best only briefly, in order to prevent damage to the treated tobacco. With the inventive preferred pulsating treatment one operates preferably at a lower temperature in the range of about 55C to 65C and an upper temperature in the range of about 75C to 95C, whereby, however, especially then if the treated tobacco is to be after-fermented, an upper temperature range of approximately 75C to 85C should not be exceeded in order not to destroy the enzyme activity required for afterfermentation.

Mellowing of the Tobacco With so-called mellowing of tobacco, that is to say, during the treatment of a tobacco which by its very nature is too sharp or acrid or which has become too sharp by virtue of having been subjected to a denicotinization treatment with a treatment medium containing ammonia, and wherein the previously mentioned tobacco mellowing is carried out at increased temperature with an ammonia-free treatment medium containing at least water vapor, the absence of any quickly determinable objective measurement value enabling monitoring and controlling the course of the treatment, and in particular the determination of the optimum point of time for the interruption of the treatment is particularly grave. This is so because the marketability of smoking tobacco is considerably dependent upon the tasteand aroma characteristics of the tobacco product. Since, as already described and discussed above, previously there was not known any analysis value which could possibly provide such control of the treatment process and suitable treatment conditions also could not be determined on the'basis of values gained from experience, since both the treatment of one and the same tobacco batches or portions in different installations as well as also the treatment of different tobacco batches or portions in one and the same installation proceeds differently as a general rule, the mellowing of tobacco through treatment with an ammonia-free at least steam or water vapor-containing treatment medium previously time and again always resulted in unpredictable and oftentimes unusable results. The prior art theoretically taught the possibility for each tobacco batch or portion to be' mellowed to carry out in an industrial installation utilized for this purpose a full-scale run for such length of time until the treated tobacco was surely overtreated and therefore strawy or flat, and then at brief time intervals to remove samples of the tobacco material which then could be tested with regard to their taste characteristics.

Surprisingly, it has now been found on the basis of the teachings of this invention that a direct correlation exists between the taste characteristics of the treated tobacco and the base content of the treatment medium leaving the tobacco which allows controlling the treatment, independently of the installation in which the tobacco is treated, on the basis of easily determinable an-- alytic data. This extremely advantageous result can be realized in that the pH-value and/or the titration value, that is, a comparison is made between the required ml 0.1 n H needed to neutralize 10 ml condensate of treatment medium departing from the tobacco at the end of treatment with that value of treatment medium condensate which under the same treatment conditions, especially with respect to temperature, pressure, flow velocity of the treatment medium and its content of water vapor, departs from the tobacco at the beginning of the treatment, and specifically directly after constant conditions have been established or regulated.

The pH-value which is a measure for the type and quantity of the bases which are contained in the treatment medium and which can be easily continuously measured is thus chosen as the primary criteria for termination of the treatment. If the critical pH-value has been reached, then, as the second criteria for the final determination of the terminal point of treatment there may be determined at short time intervals the titration value of the condensate which is a measure for the total content of the condensate of titratable basis, and similar to the pH-value, can be compared with the corresponding starting values, as above explained.

If there is desired to be obtained as the product produced in accordance with the inventive method a tobacco which is milder than the untreated tobacco, in other words if for example a tobacco which by its very nature is too sharp is to be mellowed by treatment with a water vapor-containing treatment medium, then, the pH-value of the condensate of the treatment medium leaving the tobacco directly prior to interruption of treatment, as already previously mentioned, must be smaller by at least 0.1 than the so-called -referencepH-value, which it will be recalled corresponds to the pH-value of the treatment medium condensate leaving the treated tobacco immediately following the start of treatment. In order to prevent overtreatment of the tobacco, on the other hand' treatment should be interrupted before the pI-l-value of the condensate is more than 1.0 below the reference-pH-value. It is preferable to terminatethe treatment when the condensate pH- value is below the reference pH-value by approximately 0.2 to approximately 0.5. Extremely favorable results can be obtained as a general rule if the condensate pl-l-value at the point of time of termination of the treatment is approximately 0.3 to 0.4 below the reference pH-value.

On the other hand, if a tobacco which by its very nature is sufficiently mild or possibly even too mild is initially denicotinized through the use of an ammoniacontaining treatment medium and owing to such treatment the tobacco becomes sharper than the untreated tobacco, so that following denicotinization the tobacco must again be mellowed by treating same with an ammonia-free steam-containing treatment medium, then with the method of the invention the condensate pH- value at the point of time of interruption of the mellowing treatment can be above the reference pH-value up to an amount approximating 0.5 units of pH. When carrying out this embodiment of the invention the treatment is preferably only then interrupted when the condensatepH-value is at least at a value which at most is greater by 0.2 units than the reference pl-l-value, and especially has dropped to a value which at most is the same as the reference pl-l-value and preferably up to a value of 0.3 units below the reference pH-value. For the termination of the treatment at a pH-value of the condensate which is below the reference pH-value for this embodiment of the invention the same rules and the same pH-value ranges are applicable as was the case for the previously discussed embodiment of the invention where the mellowing is not proceeded by any denicotinization while using an ammonia-containing treatment medium.

A measure for the base concentration of the treatment medium leaving the treated tobacco is the titration value of the condensate, that is the amount of 0.1 normal sulfuric acid which is necessary for neutralizing 10 ml condensate. (Since for the purposes of the invention the titration value is always compared with the socalled reference titration value, that is to say, the titration value of a condensate sample which has been obtained during discharge from the tobacco immediately after establishment or adjustment of stable conditions in the treatment system during treatment of the raw tobacco material with an ammonia-free, steam- I containing treatment medium, it is of course possible to employ for the determination of the titration value also greater or smaller condensation samples, strong acids other than sulfuric acid and titration solutions with other acid concentrations.) Since the determination of the titration value is somewhat more cumbersome than the determination of the pH-value, it is preferable when practicing the method aspects of the invention to continuously measure the pH-value, while the titration value is then only measured during critical phases of treatment, that is, particularly then when from the pH- value there can be recognized that the desired treatment condition of the tobacco undergoing treatment soon will be reached, the titration value then being determined at short-time intervals.

As previously explained, with the inventive embodiment of the method of this development, wherein a tobacco which by its very nature is too sharp is essentially only mellowed by treatment with an ammonia-free, steam or water vapor-containing treatment medium, treatment is terminated when the titration value is beneath the reference titration value by approximately 10 to approximately 30 percent preferably by approximately 15 to 25 percent and in particular about 20 percent below the reference titration value.

With the previously likewise discussed preferred embodiment of the invention in which a tobacco which is to be treated is initially denicotinized by treatment with an ammonia-containing treatment medium and therefore automatically rendered sharper, as already, explained and depending upon the type of tobacco, treatment is terminated when the titration-value during the closing mellowing treatment with an ammonia-free, steam-containing treatment medium at least has dropped to a value which is at most approximately percent of, and preferably at most approximately 1 10 percent of the reference titration value. For the interruption of the treatment with titration values which are the same as the reference titration value or below the reference titration value there are applicable the values previously mentioned for the embodiments of the inventive method serving essentially only for mellowing of the tobacco. Measures for Attaining as Uniform and Protective Treatment of the Tobacco as Possible In order to obtain as protective as possible treatment of tobacco which is sensitive to high temperatures during the practice of the method aspects of the invention the tobacco to be treated, preferably while subjected to reduced pressure, especially at a pressure in the range of approximately to 700 mm. mercury pressure (Torr), it has been found to be advantageous to vary from time to time the pressure prevailing in the treatment space of compartment during treatment, for instance in that a valve leading tothe suction line is periodically closed in each instance for 5 to 10 minutes and then again opened for approximately 10 to 20 minutes.

EXAMPLES The examples and comparative tests given hereinafter further serve to explain this invention, yet it should be understood that the invention itself is not to be considered limited to the details and numerical values given in the examples which are here presented purely by way of illustration and not limitation.

Example 1 Since publications have reported about the recirculation of the excess ammonia through the tobacco, which is comparable to a predetermined, required reaction time for freeing the nicotine of its salts, comparative tests were initially carried out in order to determine whether a longer exposure time of the gases is necessary or whether there can be obtained the same quantity of nicotine directly after passing the ammonia through the tobacco.

2,000 grams loose tobacco leaves were subdivided into two equal parts, and

a. 1,000 grams introduced into a vacuum apparatus. After evacuation to mm Hg pressure (Torr) there was introduced water vapor and 30 grams of ammonia and such was permitted to stand for 15 minutes. Thereafter, the tobacco was steamed-out for 30 minutes under vacuum conditions at 60 C. Every 3 minutes fractions were removed and analyzed. The pl-I-value and the nicotine content of the condensatewas determined.

b. In case b the other half of the tobacco was immediately steamed-out under vacuum conditions at 60 C, and during the first minutes there was simultaneously continuously introduced 30 grams of NH In both cases the moisture content of the tobacco amounted to 15 percent. l-Iere also during 30 minutes (plus the 15 minutes required during procedure a for the reaction time) fractions were removed every 3 minutes and analyzed.

The results of these tests have been charted in the following Tables I(a) and l(b) and have been graphically illustrated in FIGS. 1a and lb, respectively.

TABLE l(a) Treatment: Denicotiniration during different effective times of the gas. 15 minutes permitted to stand in a saturated NH atmosphere 30 minutes steaming-out.

ment times, that is, during the trial a 15 minutes effective time plus 30 minutes steaming, and for the trial b 15 minutes gas throughflow plus 30 minutes steaming, then there will be observed a nicotine content of 7,020 mg. in the condensate of trial b in contrast to 4,565 mg. nicotine in the condensate of trial a, that is to say 53 .78 percent more yield. Example 2 M After it was apparent from Tables l(a) and l(b) that an additional reaction time did not bring with it a correspondingly increased yield of nicotine and a larger portion of the ammonia remained unused, the question arose as to what actually is the required or economical dosage of NH;,.

There was, for instance, already proposed using the alkalinization agent (NH in an approximately 2 to 3-* fold excess of the quantity theoretically required for converting or transforming the nicotine salts.

Independent of the fact that for different tobaccos the nicotine is present in still not yet explained different pronounced bonds with different acids, the gas quantity to be used and especially the dosage something which is important for a gas which can be removed during treatment cannot be determined on the basis .of theoretical calculations. An evaluation of the test re- .sults carried out in Example 1 (cf., in particular, Table l(b) starting from fractions 5-10) showed that the pH- value of the condensate and the corresponding nicotine quantity are in a narrow correlation to one another. In other words, the optimum nicotine yield is present at a with water vapor and with NH 30 minutes steaming-out. treatment temperature 65C.

Tobacco Type Treated: Geudertheimer HGT 65 leaf tips.

Quantity: 1 kg.

Time Quantity Temp. Condensate Nicotine Comments Fraction Min. ml C pH (mg/500 ml) 6 18 500 65 11.3 694 7 21 500 r 65 11.2 460 8 24 500 65 11.707, 3 37 9 27 500 65 10.8 277 1 10 10 30 500 65 10.7 234 6080 ll 3 3 500 v 65 10.7 215 12 36 500 65 10.6

13 39 500 65 10.5 193 .I4 42 500 65 10.5 159 l 1 5 15 45 500 65 10.5 137 70l 0 From Tables l(a) and l(b) it is apparent that during the trial a where the tobacco previously was permitted to stand for 15 minutes in an annomia atmosphere, for the purpose of checking the effect of the reaction time,

after 30 minutes steaming out, with the ten fractions pI-I-value of 11.6 to 11.7, at lower pH-values on the oth r hasdlhi asasiissqns dsebaAs am;

A homogeneous tobacco sample which had been subdivided into two equal portions, each of 200 grams, had passed therethrough under vacuum conditions vapor. mixtures at 60C for different pH-values. The condensate was analyzed at individual fractions. The results of these tests have been graphically plotted in FIGS. 2a and 2b and clearly indicate that the pH of the condensate plays a decisive role for the nicotine yield and that at 60C a pH of l 1.7 affords the optimum yield. A 2 to 3-fold, or even greater fold increased ammonia dosage cannot increase the pH and accordingly the yield, rather only leads to unnecessary gas usage.

From the previously mentioned publications it is clearly apparent that the nicotine yield for constant distillation conditions reduces with progressive time. Reduction of the yield is particularly significant at pH- values exceeding 10. The maximum nicotine concentration of the condensate at a pH of 1 1.7 and approximately 200 mm Hg mercury (Torr) pressure, and at a temperature of 63C amounted to 0.1 percent. Example 3 Continuous and lmpulse"-Treatment Since for ammonia-absorption, something which is important for the nicotine yield, lower temperatures, which it is to be mentioned simultaneously render possible a relatively protective tobacco treatment, are more desirable than higher temperatures, it appears important to examine whether through temperature-and pressure and concentration-changes the yield can be thermore, attention is invited to the bend or knee points indicated at and Kp in the pH-curves and the denicotinization and nicotine yield curves of FIGS. 4a and 4b, the significance of which for the control of the high temperature phases has already been explained above.

TABLE [1(a) Treatment: Denicotinimtion at periodic temperature increases and discontinuous gas dosages. Treatment temperature Quantity: 200 grams. Size or Format: 2+2 cm ac- Time Quantity Temp. Conden- Nicotine Comments tion Min. ml -C' sate pH (mg/250 ml) 1 2.45 250 65 11.7 816 Total Nicotine 2 2.45 250 65 11.7 678) 65C NH, 5170 mg. 3 2.45 250 65 11.7 521) Fraction l-12 TABLE 11(b) temperature 6580C. Quantity: 200 grams. Size or Format: 2+2 cm.

Frac- Time Quantity Temp. Conden- Nicotine Comments tion Min. ml. C sate pH (mg/250 ml) 1 2.45 250 65 1 1.7 875 Fraction 12 61 10 mg. 2 2.45 250 65 l 1.7 731 l 80 NH; 10 2.45 250 80 11.4 373 l 11 2.45 250 65 11.7 176 1 65 1ncreased during the treatment time. The comparatlve tests set forth in Tables [1(a) and 11(b) and corresponding to theresults graphically illustrated in FIGS. 3a and Upon repeating these comparative tests with a respective 2 kilograms likewise homogeneous tobacco material, wherein the tobacco on the one hand was the tobacco was continuously examined with regard to its pH-value and titration value. Additionally, the employed quantity of ammonia was determined and the nicotine yield measured at the vapor condensate.

set forth in Table III. The nicotine content of the untreated tobacco TABLE III amounted to 1.33 percent, corresponding to 3.99

grams (21.9 mM) nicotine in 300 grams tobacco. T D T 0 C The results obtained during these tests have been colreatment: enicotinization reatrnent temperature: 6 constant Tobacco Type: Bcneventano (1125 l) lercted In followlng Table Quantity: 2 kg 1 Example 5 Fraction Time Quantit Tem C d t N t' i 1 y on ensa 6 52 ,5 (Directed and controlled den1cot1n1zat1on of raw to- 0 3 bacco) l 2 60 I mg The nicotine content of 100 k tobacco (Rio 2 20 3.3 60 11.7 19.6 g 20 3 3.4 60 11.7 19.5 Grande) havmg a starting value of 1.54 percent n1co- 60 8200 mg tine should be reduced to 0.8 percent. This means that Treatment; Denicotinizatign pulsati "ti 740 grams nlcotme must be removed from the tobacco. Type: Beneventano (1 128 l) 7 Quantity? 2 kg Fraction Time Quantity Temp. Condensate Nicotine For thls purpose 100 kg tobacco Introduce? mto 25 ml an apparatus and treated for approx1mately 5 minutes I 10 I 5 60 H 7 33 5 mg with saturated water vapor at a temperature of 65C. A 2 3 g0 part of the water vapor emanating from the tobacco g g g8 was condensated and the pH-value of this condensate 5 10 23 60 11,7 measured. Additionally, 10 ml of this condensate was f; {I :8 titrated with 0.1 n sulfuric acid. The values amounted 8 3 80 25 to 9.8 pH and 1.85 ml'H SO 0.1n. Now ammonia gas 10 9 2.2 60 11.7 17.7 was added to the water vapor until the condensate of 63 101300 mg the treatment medium escaping from the tobacco had a pH-value of l 1.3 and (for 10 ml condensate) a titra- TABLE IV Con- Ratio Denico- Test den- Ammonia Nicotine of Continization No. sate addition in yield in Sumed in pl-:- mg and g (mM) mg and g (mM) E1132. 92 V21 U8 1cot1ne present in tobacco 1 11.1 820 mg (48.3) 975 mg (6.0) r 1.94 24.1 2 11.7 14.25 g (839.8) 2.18 g(l3.5) 33.73 54. 3 12.0 2.54 g 15.7 86.75 64.0

The greatest yield was obtained at 80C. As already previously, mentioned, this relatively high treatment temperature however, when employed durmg longer time periods has a negative effect upon the structure and quality of the tobacco. I

During the so-called pulsating treatment there is obtained 10,300 milligrams nicotine in contrast to 8,100

milligrams during the treatment variant employing aconstant temperature of 60C. The increased yield therefore amounted to 27.2 percent.

It is here to be mentioned that the temperature 1n-. creases were only always briefly carried out (a total of 13 minutes for a treatment time of 60 minutes). The quality of the tobacco was judged to be thebest wlth this pulsating treatment.

Example 4 in order to further examine the dependency of the denicotinization effect of the ammonia dosage to the treatment medium three further tests were carried out under the following conditions:

In each instance 300 grams homogeneous clgar 1nserts (Kentucky) were treated for minutes with a quantity of water vapor producing a total of 1,000 ml condensate, treatment was carried out at a temperature of 60C under reduced pressure conditions, and the quantity of ammonia being varied from test to test. The condensate of the treatment medium emanating from tion value of 45 ml 0.1 n H 80 had been reached. The

steam or water vapor emanating from the tobacco and charged with nicotine is freed from the ammonia and nicotine in a heated sulfuric acid-absorber. After a treatment time of 1 hour of the above mentioned condition the volume of sulfuric acid in the absorber was determined and an aliquot sample removed. At this sample the nicotine content was determined by means of a Technicon-Autoanalyzer. With a quantity of absorption agent amounting to 80 liters and a nicotine content of 0.74 percent of nicotine removed at this point of time from the tobacco amounted to 592 grams. These measurements now -were repeated approximately every 10 minutes. After a further 40 minutes treatment time there was determined at the absorption agent a total nicotine content of 720 grams. Thereafter, the dosage of ammonia was stopped, the temperature increased to C and the tobacco further treated with pure steam or water vapor for the purpose of driving out the ammonia remaining in the tobacco. The condensated portion. of the treatment medium escaping from the tobacco was delivered past a pl-l-electrode and thus the pH-value continuously measured and recorded by a suitable recording instrument. After 50 minutes treatment with pure steam, the vgpor cende'fi I sate possessed a pH-value of9.65rFofTibtaining more precise results the titration value of the condensate was also determined in the above described manner, resulting in a value of 3.6 ml l-I- SO 0.1 n. The determination of the titration value was carried out from this point of time every 5 minutes. After a further minutes treatment time the vapor condensate possessed a pH-value of 9.6 and a titration value of 1.75 ml 0.1 n H 80 The total nicotine content at the absorption agent amounted to 752 grams. The nicotine content of the treated tobacco was thus reduced to 0.78 percent. Example 6 In order to be able to demonstrate the differences between the inventive controlled mode of operation and the previously employed method of denicotinization and/or mellowing of tobacco, where the treatment conditions, especially the duration of the mellowing treatment was only carried out on the basis of empirical values", a further series of comparative tests was carried out where six different tobacco types were each denicotinized and mellowed or only mellowed, both by carrying out the method of the invention (determining the duration of the treatment with steam according to the condensate pI-I-value and the titration value) as well as also by the conventional techniques (duration of the treatment with steam on the basis of empirical values, amounting in each case to 30 minutes, with the exception of test 512 where, because of the very poor smoke result test during the control, mellowing was carried outfor 150 minutes).

All of the tobacco types were subjected both before Inhalation: very pronounced pronounced average slight very slight Sharpness: very sharp sharp average trace of sharpness no sharpness Character plus Aroma: flat little aroma average aroma good aroma very good aroma 1111111111 --Mua$-u| Taste plus general impression: poor not open coated not quite clean open and clean 1111111111 -mwtsut The results of these trials have been collected together in Table VI, from which can be seen that the and after treatment to an organoleptic qualitative smoke judgment or'grading for all of the tobaccos TABLE VI Starting Phase Mellowing Phase Tobaggg Analysis Smoke Grading Vapor pH of Titration of Duration of Duration of pH of Titration of NH- Nicotine Treatment Vapor 10 ml Treatment Treatment Vapor 10 ml (Min) Condensate Condensate with with Pure Condensate Condensate (Reference with Vapor- Water wit pH-Value) H SO 0.l N Ammonia Vapor H SO O.1 N

in ml Mixture (Min) (ml) (Reference (Min) Titration Value) a h u b u h Rio Grande 6788 Denicotinization Treatment 5 9.8 4.5 120 9.6 3.0 1.27 0.93 2.33 1.18 4.5 2.0 120 30 1.27 1.23 2.33 1.28 4.5 3.5

Geudertheimer OGT 64 Denicotinization Treatment 5 9.9 4.8 Y 120 9.6 2.8 1.30 0.89 2.45 122 4.5 1.5 30 1.30 1.61 2.43 142 4.5 5.0K

Rio Grande 8092 Denicotinization Treatment 5 9.6 3.8 60 9.4 3.1 1.12 0.90 3.24 2.08 5.0 2.0 140 30 1.15 1.82 3.21 2.32 5.0 5.0K

' Paraguay 18 B Mellowing 4 Treatment '5 98 4.8 60 9.5 2.4 1.42 0.98 1.34 1.11 4.0 1.5 3O 1.43 1.21 1.30 1.20 4.0 3.0

Geudertheimer HOT 65 Mellowing Treatment "5 10.1 5.9 80 9.5 3.1 1.87 0.85 0.97 0.83 5.0 1.5 1.85 0.43 0.97 0.63 5.0 4.5 L

Burley HOT 65 Mellowing Treatment 5 10.0 5.4 70 9.6 2.9 1.51 0.92 1.13 1.02 4.5 1.5 30 1.52 1.34 1.10 1.08 4.5 4.0 K

"untreated treated Inventive Method Conventional Method NOTE: 1. Constant Conditions for all Trials Vapor: 1.5 kg/min. Temp; 60C 0 Tobacco: 100 kg 2. best grade=l poorest grade=5 K=irritating smoke L=flat or empty aroma Example 7 For the purpose of denicotinization 100 kg tobacco was introduced into an installation suitable for the flow of the treatment medium through the tobacco and for approximately 5 minutes saturated steam at a tempera-' ture of 60C was permitted to flow through the tobacco. A portion of the steam emanating from the tobacco was condensated and the pH-value thereof was measured. Similarly, 10 ml condensate was titrated with 0.1 n H SO in order to'obtain characteristic values concerning the volatile bases of the untreated tobacco. Now ammonia gas was introduced into the steam until the vapor condensate escaping out of the tobacco possessed a pH-value of approximately 1 l and for l ml condensate there was obtained a titration value of approximately 45 ml 0.1 n H 50 After 45 minutes the temperature of the vapor was raised to 70C and after a further 45 minutes to 80C, then held for an additional 45 minutes at this temperature. Throughout the entire previous treatment times the alkalinity of the treatment medium was held at the desired values through appropriate infeed dosage of ammonia.

After these three treatment stages the ammonia dosage was interrupted and the temperature increased to approximately 85C and, for the purpose of driving out the ammonia which remained in the tobacco, pure steam was permitted to flow through the tobacco. At time intervals of approximately 5 minutes there was determined the pH-value and the alkalinity of the conden sate of the treatment medium emanating from the tobacco. After a further 60 minutes treatment time the vapor condensate exhibited a pH-value which was less by 0.2 units of pH and a titration value which was less by 2.5 ml 0.1 n H SO per ml condensate, than the starting values prior to the addition of ammonia. The flow direction of the treatment medium was reversed every minutes. Example 8 For the purpose of mellowing 100 kg tobacco such was placed into an installation suitable for the flow of the treatment medium through the tobacco. For approximately 5 minutes saturated steam at a temperature of 60C was passed through the tobacco. Now analogous to the procedures of Example 1 the characteristic values of the volatile bases of the untreated to bacco were determined. Then the temperature of th steam was increased within 5 minutes to 100C, held at this value for approximately 2 minutes, and then within 5 minutes again brought back to 60C, and held at this temperature for 8 minutes. These temperature changes were repeated 5 times. The temperature-intervals were automaticallyv programed. A portion of the steam or water vapor emanating from the tobacco was condensated and the condensate transferred by means of a suitable device to the electrode of a pH-measuring device of standard design and the pl-l-value continuously measured. In similar fashion 10 ml of this condensate was titrated with 0.1 n H SO something which also can be automated, in order to obtain a continuous measurement. After a treatment time of 1 hour and 45 minutes the vapor condensate emanating from the tobacco exhibited a pl-l-value which was lower by the amount of 0.3 units of pH and a titration value which was lower by the amount of 3 ml 0.1 n H SO per 10 ml condensate, than the starting values of the untreated tobacco. The flow direction of the treatment medium was reversed every 20 minutes.

, Example 9 For denicotinization of the tobacco one also proceeds in the fashion that after measuring the starting values of the untreated tobacco the temperature course of the treatment medium was programed in accordance with the teachings of Example 2. The ammonia was only dosed-in at the lower temperatures and the addition always interruped upon reaching the higher temperature. The determination of the alkalinity value of the vapor condensate emanating from the tobacco was performed analogous to the teachings of Example 2. The pH-value of approximately 1 l was maintained for 2 hours, then the infeed of ammonia was shut-off. The ammonia remaining in the tobacco was driven-off'with pure steam or water vapor until the vapor condensate emanating from the tobacco had a pl-l-value which was lower by the amount 0.3 and a titration value lower by the amount 3.5 ml 0.1 n H SO per 10 ml condensate than at the beginning of treatment. The drive-off time amounted to 45 minutes. Also, for this treatment the flow direction of the treatment medium was reversed every 20 minutes.

While there is shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

Accordingly, what is claimed is:

l. A method for denicotinization and mellowing of tobacco, comprising the steps of passing through the tobacco a gaseous treatment medium containing at least ammonia and steam for denicotinization purposes, then passing through the tobacco an ammoniafree, steam-containing gaseous treatment medium for tobacco mellowing purposes, controlling the ammonia concentration during the denicotinization step such that the pl-I-value of the condensate of the treatment medium departing from the tobacco is in a range between approximately 11.0 and 12.0, and for tobacco mellowing passing the ammonia-free, steam-containing treatment medium through the tobacco for such length of time until the pl-I-value of the condensate of the treatment medium departing from the tobacco is in a range of approximately 1.0 units of pH below to approximately 0.5 units of pH above a reference-pH- value of the condensate of the treatment medium obtained under the same conditions prior to tobacco denicotinization.

2. The method as defined in claim 1, wherein during denicotinization there is controlled the delivery of ammonia such that the pH-value of the condensate of the treatment medium departing from the tobacco is in a range between approximately 1 1.0 and 12.0

3. The method as defined in claim 1, wherein the throughflow of the ammonia-free, steam-containing treatment medium through the tobacco during mellowing is carried out for such length of time until the pH- value of the condensate of the treatment medium departing from the tobacco at most is about 0.2 units of pH above the reference pH-value.

4. The method as defined in claim 3, wherein the throughfiow of the treatment medium is carried out for such length of time until the pH-value of the condensate of the treatment medium departing from the tobacco is at least approximately 0.3 units of pH below the reference pH-value.

5. The method as'defined in claim 1, including the step of at least increasing for certain time periods the temperature of the treatment medium.

6. The method as defined in claim 5, including the step of controlling the temperature of the treatment medium at the beginning of its flow through the tobacco so as to be less than 75C, and alternately increasing and again decreasing the temperature of the treatment medium during its flow through the tobacco such that each temperature increase is greater than the following temperature decrease.

7. The method as defined in claim 6, including the step of maintaining the temperature of the treatment medium for 5 to 20 minutes at a higher value and for to minutes at a lower value, wherein the amount of each temperature increase is the same as each temperature decrease.

8. The method as defined in claim 6, including the step of introducing the ammonia during periods of lower temperature.

9. A method for denicotinization and mellowing of tobacco comprising the steps of passing through the tobacco a gaseous treatment medium containing at least ammonia and steam for denicotinization purposes, forming a condensate and determining the titration value of said condensate, then controlling the ammonia concentration in the ammonia steam treatment medium during the denicotinization step such that said condensate when titrated as 10 ml sample indicates an acid consumption in a range amounting to approximately 45 to 80 ml 0.1 acid, and then passing through the tobacco, an ammonia-free, steam-containing gaseous treatment medium for tobacco mellowing purposes, said ammonia-free, steam-containing medium being passed through the tobacco for such length of time until a sample of the condensate from this latter treatment medium departing from the tobacco, upon titration thereof, indicates an acid consumption which amounts to 70 to l 10 percent of an initial reference titration value which is obtained prior to denicotinization and which is of the same size sample of the initial condensate.

10. The method as defined in claim 9, wherein the infeed of ammonia during denicotinization is controlled such that the acid consumption of a 10 ml sample of the treatment medium departing from the tobacco lies between approximately 45 and 80 ml 0.1 n acid.

11. The method as defined in claim 9, including the step of at least increasing for certain time periods the temperature of the treatment medium.

12. The method as defined in claim 11, including the step of controlling the temperature of the treatment medium at the beginning of its flow through the tobacco so as to be less than C, and alternately increasing and again decreasing the temperature of the treatment medium during its flow through the tobacco such that each temperature increase is greater than the following temperature decrease.

13. The method as defined in claim 11, including the step of maintaining the temperature of the treatment medium for 5 to 20 minutes at a higher value and for 10 to 20 minutes at a lower value, wherein the amount of each temperature increase is the same as each temperature decrease.

14. The method as defined in claim 12, including the step of introducing the ammonia during periods of lower temperature.

15. The method as defined in claim 9, including the step of controlling the temperature of the treatment medium at the beginning of its flow through the tobacco so as to be less than 75C, and alternately increasing and again decreasing the temperature of the treatment medium during its flow through the tobacco such that each temperature increase is greater than the following temperature decrease.

16. The method as defined in claim 9, including the step of maintaining the temperature of the treatment medium for 5 to 20 minutes at a higher value and for 10 to 20 minutes at a lower value, wherein the amount of each temperature increase is the same as each temperature decrease.

17. The method asdefined in claim 15, including the step of introducing the ammonia during periods of lower temperature.

18. A method for mellowing tobacco, comprising the steps of passing an ammonia-free, steam-containing gaseous treatment medium through the tobacco, passing the treatment medium through the tobacco for such length of time until the pH-value of the condensate of the treatment medium departing from the tobacco is in a range of approximately 0.1 units of pH to approximately 1.0 units of pH below a reference-pH-value of condensate of the treatment medium obtained under the same conditions prior to mellowing.

19. The method as defined in claim 18, wherein the treatment medium is passed through the tobacco for such length of time until the pH-value of the condensate of the treatment medium departing from the tobacco is approximately 0.2 units of pH to approximately 0.5 units of pH below the reference pH-value.

20. The method as defined in claim 19, including the step of passing the treatment medium through the tobacco for such length of time until the pH-value of the condensate of the treatment medium departing from the tobacco is approximately 0.3 units of pH to approximately 0.4 units of pH below the reference pH-value.

21. The method as defined in claim 18, including the step of at least increasing for certain time periods the temperature of the treatment medium.

22. The method as defined in claim 21, including the step of controlling the temperature of the treatment medium at the beginning of its flow through the tobacco so as to be less than 75C, and alternately increasing and again decreasing the temperature of the treatment medium during its flow through the tobacco in a manner such that each temperature increase is greater than the following temperature decrease.

23. The method as defined in claim 21, including the step of maintaining the temperature of the treatment medium for to 20 minutes at a higher value and for to minutes at a lower value, wherein the amount of each temperature increase is the same as each temperature decrease.

24. A method for mellowing tobacco, comprising the steps of passing an ammonia-free, steam-containing treatment medium through the tobacco, controlling the flow of the treatment medium through the tobacco for such length of time until a sample of the condensate of the treatment medium departing from the tobacco during titration thereof exhibits an acid consumption which is at least approximately lower by the value of 5 than a reference titration value determined by titrating a condensate sample of the treatment medium departing from the tobacco under the same conditions prior to tobacco mellowing.

25. The method as defined in claim 24, including the step of at least increasing for certain time periods the temperature of the treatment medium.

26. The method as defined in claim 25, including the step of controlling the temperature of the treatment medium at the beginning of its flow through the tobacco so as to be less than 75C, and alternately increasing and again decreasing the temperature of the treatment medium during its flow through the tobacco such that each temperature increase is greater than the following temperature decrease.

27. The method as defined in claim 24, including the step of maintaining the temperature of the treatment medium for 5 to 20 minutes at a higher value and for 10 to 20 minutes at a lower value, wherein the amount of each temperature increase is the same as each temperature decrease.

28. A method for mellowing tobacco and for reducing the nicotine content thereof comprising the steps:

E. continuing denicotinization for a time sufficient to reduce the nicotine content to a desired level,

F. Contacting the tobacco with ammonia-free steam for a time sufficient to reduce the pH-value of the condensate emanating from the tobacco to from about 1.0 units below and from about 0.5 units above the reference-pH-value established in steps A-C inclusive. 

2. The method as defined in claim 1, wherein during denicotinization there is controlled the delivery of ammonia such that the pH-value of the condensate of the treatment medium departing from the tobacco is in a range between approximately 11.0 and 12.0
 3. The method as defined in claim 1, wherein the throughflow of the ammonia-free, steam-containing treatment medium through the tobacco during mellowing is carried out for such length of time until the pH-value of the condensate of the treatment medium departing from the tobacco at most is about 0.2 units of pH above the reference pH-value.
 4. The method as defined in claim 3, wherein the throughflow of the treatment medium is carried out for such length of time until the pH-value of the condensate of the treatment medium departing from the tobacco is at least approximately 0.3 units of pH below the reference pH-value.
 5. The method as defined in claim 1, including the step of at least increasing for certain time periods the temperature of the treatment medium.
 6. The method as defined in claim 5, including the step of controlling the temperature of the treatment medium at the beginning of its flow through the tobacco so as to be less than 75*C, and alternately increasing and again decreasing the temperature of the treatment medium during its flow through the tobacco such that each temperature increase is greater than the following temperature decrease.
 7. The method as defined in claim 6, including the step of maintaining the temperature of the treatment medium for 5 to 20 minutes at a higher value and for 10 to 20 minutes at a lower value, wherein the amount of each temperature increase is the same as each temperature decrease.
 8. The method as defined in claim 6, including the step of introducing the ammonia during periods of lower temperature.
 9. A method for denicotinization and mellowing of tobacco comprising the steps of passing through the tobacco a gaseous treatment medium containing at least ammonia and steam for denicotinization purposes, forming a condensate and determining the titration value of said condensate, then controlling the ammonia concentration in the ammonia steam treatment medium during the denicotinization step such that said condensate when titrated as 10 ml sample indicates an acid consumption in a range amounting to approximately 45 to 80 ml 0.1 acid, and then passing through the tobacco, an ammonia-free, steam-containing gaseous treatment medium for tobacco mellowing purposes, said ammonia-free, steam-containing medium being passed through the tobacco for such length of time until a sample of the condensate from this latter treatment medium departing from the tobacco, upon titration thereof, indicates an acid consumption which amounts to 70 to 110 percent of an initial reference titration value which is obtained prior to denicotinization and which is of the same size sample of the initial condensate.
 10. The method as defined in claim 9, wherein the infeed of ammonia during denicotinization is controlled such that the acid cOnsumption of a 10 ml sample of the treatment medium departing from the tobacco lies between approximately 45 and 80 ml 0.1 n acid.
 11. The method as defined in claim 9, including the step of at least increasing for certain time periods the temperature of the treatment medium.
 12. The method as defined in claim 11, including the step of controlling the temperature of the treatment medium at the beginning of its flow through the tobacco so as to be less than 75*C, and alternately increasing and again decreasing the temperature of the treatment medium during its flow through the tobacco such that each temperature increase is greater than the following temperature decrease.
 13. The method as defined in claim 11, including the step of maintaining the temperature of the treatment medium for 5 to 20 minutes at a higher value and for 10 to 20 minutes at a lower value, wherein the amount of each temperature increase is the same as each temperature decrease.
 14. The method as defined in claim 12, including the step of introducing the ammonia during periods of lower temperature.
 15. The method as defined in claim 9, including the step of controlling the temperature of the treatment medium at the beginning of its flow through the tobacco so as to be less than 75*C, and alternately increasing and again decreasing the temperature of the treatment medium during its flow through the tobacco such that each temperature increase is greater than the following temperature decrease.
 16. The method as defined in claim 9, including the step of maintaining the temperature of the treatment medium for 5 to 20 minutes at a higher value and for 10 to 20 minutes at a lower value, wherein the amount of each temperature increase is the same as each temperature decrease.
 17. The method as defined in claim 15, including the step of introducing the ammonia during periods of lower temperature.
 18. A method for mellowing tobacco, comprising the steps of passing an ammonia-free, steam-containing gaseous treatment medium through the tobacco, passing the treatment medium through the tobacco for such length of time until the pH-value of the condensate of the treatment medium departing from the tobacco is in a range of approximately 0.1 units of pH to approximately 1.0 units of pH below a reference-pH-value of condensate of the treatment medium obtained under the same conditions prior to mellowing.
 19. The method as defined in claim 18, wherein the treatment medium is passed through the tobacco for such length of time until the pH-value of the condensate of the treatment medium departing from the tobacco is approximately 0.2 units of pH to approximately 0.5 units of pH below the reference pH-value.
 20. The method as defined in claim 19, including the step of passing the treatment medium through the tobacco for such length of time until the pH-value of the condensate of the treatment medium departing from the tobacco is approximately 0.3 units of pH to approximately 0.4 units of pH below the reference pH-value.
 21. The method as defined in claim 18, including the step of at least increasing for certain time periods the temperature of the treatment medium.
 22. The method as defined in claim 21, including the step of controlling the temperature of the treatment medium at the beginning of its flow through the tobacco so as to be less than 75*C, and alternately increasing and again decreasing the temperature of the treatment medium during its flow through the tobacco in a manner such that each temperature increase is greater than the following temperature decrease.
 23. The method as defined in claim 21, including the step of maintaining the temperature of the treatment medium for 5 to 20 minutes at a higher value and for 10 to 20 minutes at a lower value, wherein the amount of each temperaTure increase is the same as each temperature decrease.
 24. A method for mellowing tobacco, comprising the steps of passing an ammonia-free, steam-containing treatment medium through the tobacco, controlling the flow of the treatment medium through the tobacco for such length of time until a sample of the condensate of the treatment medium departing from the tobacco during titration thereof exhibits an acid consumption which is at least approximately lower by the value of 5 than a reference titration value determined by titrating a condensate sample of the treatment medium departing from the tobacco under the same conditions prior to tobacco mellowing.
 25. The method as defined in claim 24, including the step of at least increasing for certain time periods the temperature of the treatment medium.
 26. The method as defined in claim 25, including the step of controlling the temperature of the treatment medium at the beginning of its flow through the tobacco so as to be less than 75*C, and alternately increasing and again decreasing the temperature of the treatment medium during its flow through the tobacco such that each temperature increase is greater than the following temperature decrease.
 27. The method as defined in claim 24, including the step of maintaining the temperature of the treatment medium for 5 to 20 minutes at a higher value and for 10 to 20 minutes at a lower value, wherein the amount of each temperature increase is the same as each temperature decrease.
 28. A method for mellowing tobacco and for reducing the nicotine content thereof comprising the steps: A. contacting the tobacco with steam, B. condensing a small portion of the steam, C. analyzing the condensate for the purpose of determining a reference-pH-value, D. contacting the tobacco with a gaseous mixture comprising steam and ammonia for reducing the nicotine content of the tobacco, said gaseous mixture being regulated to provide a sufficient concentration of ammonia such that the condensate after contact with the tobacco has a pH-value between 11 and 12, E. continuing denicotinization for a time sufficient to reduce the nicotine content to a desired level, F. Contacting the tobacco with ammonia-free steam for a time sufficient to reduce the pH-value of the condensate emanating from the tobacco to from about 1.0 units below and from about 0.5 units above the reference-pH-value established in steps A-C inclusive. 